This invention relates to the packaging and storing of aqueous developable photoresists. More particularly it relates to the reduction of edge fusion in packaged photoresists.
Aqueous developable photoresists are superior to non-aqueous developable resists, since aqueous developable photoresists employ water-base developing and stripping solutions, which avoid the environmental problems and high costs associated with the organic solvents and solvent additives needed to develop and strip non-aqueous resists.
Aqueous developable photoresists are typically packaged and stored in roll form as a laminate of the photoresist composition sandwiched between a flexible film support and a protective cover sheet. When packaged in this form the photoresist has a tendency to "cold flow". U.S. Pat. No. 3,867,153 hypothesizes that cold flow is caused by increases in temperature and/or pressure. Cold flow results in the photoresist oozing out from between successive layers of the film and cover sheet and fusing on the edge of the roll, a phenomenon known as "edge fusion". When an edge fused roll is unrolled, chips of the photopolymer may break off, and some of the film may delaminate from its support film, which interferes with proper imaging when the photoresist is exposed and developed. A fused roll is, therefore, defective and results in increased costs to either the user, who cannot use the defective portion of the roll, the seller, who must replace the defective roll, or both. Preventing edge fusion is, therefore, desirable in cost savings related to the use and sale of photoresist compositions.
Reducing edge fusion by reducing the temperature surrounding stored photoresists and by protecting the resists from direct pressure with improved packaging have not been completely successful, and are expensive.
Reducing edge fusion is claimed in U.S. Pat. No. 3,867,153 to have been achieved by irradiating the edges of the photoresist laminate and is also claimed by adding specific compounds to the photoresist composition as shown in U.S. Pat. Nos. 4,239,849 and 4,293,635. However, both of these methods have their disadvantages; significant cost increases in production result from using either method, and irradiating makes the photoresist in the radiation exposed edges hard and, therefore, useless for photoimaging.